The disclosure relates to an exhaust treatment device, and in particular, an exhaust treatment device with a mat support having a relief slot.
Various types of exhaust treatment devices, e.g., catalytic converters, catalytic absorbers, diesel particulate traps, non-thermal plasma conversion devices, and the like, are employed in the treatment of exhaust gas streams in vehicles. These devices are employed to treat environmentally unfriendly exhaust gas elements, e.g., hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), carbon, and/or soot. A typical catalytic converter, for example, comprises a catalyst disposed on a catalytic substrate. An end-cone is disposed in fluid communication with the catalytic substrate to provide a conduit between the catalytic substrate and the rest of the exhaust system. This combination of catalyst, catalytic substrate and attached end-cone forms a catalytic substrate subassembly, (hereinafter subassembly). Sandwiched in-between a shell and the subassembly is a mat support.
The mat support serves a number of functions. The mat support insulates the shell from both the high exhaust gas temperatures, and the heat generated by the exothermic catalytic reaction occurring within the catalytic substrate subassembly. The heat retained by the mat support also aids in maintaining the high temperatures necessary for the catalytic reaction to efficiently proceed. In addition, the mat support enhances the structural integrity of the subassembly by conveying compressive forces to the subassembly. These compressive forces reduce axial movement of the catalytic substrate within the shell and thus, retain the substrate and end-cones properly in place. The mat support shape and composition, thus, have a substantial impact on the operation and integrity of the catalytic converter as a whole.
In order to provide adequate support and insulation, the mat support is uniformly disposed around, and in contact with the subassembly. However, the end-cones of a catalytic converter, which may be conical in shape, are not often symmetrical about any one axis due to space limitations and other factors. These non-uniform shapes do not lend themselves to being uniformly covered by the mat support in the form of a flat sheet. Insulation and support of catalytic converter end-cones thus, requires a compromise between the lower cost option of providing intimate contact of an irregular shape with a mat support formed from a flat sheet, verses the higher cost option of pre-forming a molded insulation cover, often from a more expensive material.